Figure 1: Graphene enables valleytronics
Valleytronics is a portmanteau in which the term ‘valley’ refers to a supplementing degree of liberation for electrons. Electrons are popularly analysed on the basis of two degrees of freedom, or characteristics have made achievable our computer age – spin and charge. Electronics have over the years exploited the charge of electrons to create gadgets that can switch off or on. And presently, we have also witnessed the spin of electrons leveraged; researchers have transformed circuits based on this feature spintronics.
Both spintronics and electronics have their weaknesses and strengths when it is about establishing the off-on states that are extremely critical for digital logic. So scientists have been in hunt of another degree of liberation in electrons that neglect those weaknesses and enhance the strengths. Instead of resting on the spins of electrons or their current, valleytronics exploits their level of energy in consideration to their momentum.
Pioneering exploration of the valley instigates in earlier 2007 when scientists initially discovered that the presently introduced 2-D substance graphene could sort holes and electrons according to which valley they occupied. Prior to this research, holes and electrons had only been detected occupying distinct valleys at random.
Now Jun Zhu, the associate lecturer of physics at Penn State, who headed most of this research, considers such experimental results offers a virtual approach to regulating the momentum of electrons and recognizing which valley they finally occupy. As a demonstration, Zhu offers a useful metaphor for visualizing valleytronics. He suggests of electrons as automobiles and the valleys wither being red or blue.
As per the details of the research, the Penn State group was potential enough to route the electrons by placing a group of gates below and above the bilayer graphene sheet and then coating an electrical field perpendicular to the plane.
“By placing a positive voltage on one of the side and a negative voltage on the other, a band-gap gets open in bilayer graphene, which it does not usually have,” explains Jing Li, a doctoral student who performed the research. “In the middle or between two sides, we have a physical gap of about 70 nanometers.”
Conclusion – “It is quite incredible that such states can be prepared in the interior of an insulating bilayer graphene sheet, utilizing just a few gates,” says Zhu. “They are not up till now resistance-free, and we are performing more researches to comprehend where resistance might come from. We are also focusing on developing valves that regulate the flow of electron based on the colour of the electrons.” While the scientists conclude that this experiment is still extremely a long passage from developing real-world valleytronics gadgets, it does offer a research framework on which the further enhancement of the technology.